Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Educational Research Cognition and Development

First Committee Member

E M. Nussbaum

Second Committee Member

Gale M. Sinatra

Third Committee Member

Gregory J. Schraw

Fourth Committee Member

Matthew S. Lachniet

Number of Pages



The Intergovernmental Panel on Climate Change (2007) reported a greater than 90% chance that human activities are responsible for global temperature increases over the last 50 years, as well as other climatic changes. The scientific report also states that alternative explanations (e.g., increasing energy received from the Sun) are less plausible than human-induced climate change. These climate scientists have made their plausibility judgment--which I define as the relative potential truthfulness of alternative explanations--based on the evaluation and coordination of multiple lines evidence with competing theoretical perspectives.

Climate change is a highly relevant and gravely serious topic; in an educational setting, climate change also presents an opportunity for students to learn about fundamental scientific principles and how scientists construct knowledge. However, students may be neither naturally evaluative when learning about controversial topics, such as climate change, nor reflective while engaging in judgments about knowledge and knowing (King & Kitchener, 2004), such as plausibility judgments. The purpose of this study was to examine how plausibility judgments and knowledge about human-induced climate change transform during instruction that promotes critical evaluation abilities.

An instructional scaffold--called a model evidence link (MEL) diagram-- was used in this study. The MEL allowed students to weigh the strength of connections between two alternative models of climate change (i.e., the scientifically accepted model of human-induced climate change and a popular skeptics' model that climate change is caused by increases in the Sun's energy). The results revealed that treatment group participants who used the MEL diagram experienced a significant shift in their plausibility judgments toward the scientifically accepted model. This shift was accompanied by significantly greater postinstructional knowledge of human-induced climate change, with treatment group participants demonstrating reconstruction of knowledge about the causes of climate change to be more consistent with scientific understanding. Moderate to large effect sizes characterized these changes in treatment group participants' plausibility perceptions and understanding. A comparison group of students who experienced a climate change activity that is part of their normal curriculum did not experience statistically significant changes.

The results from this dissertation study, along with previous studies that I and my colleagues have conducted (see, for example, Lombardi & Sinatra, 2012), helped to inform the development of a model on the role of the plausibility judgment in conceptual change. This model has the potential to guide further research that will help educators better understand the mechanisms in conceptual change and guide instructional practices to promote knowledge reconstruction on scientific topics of great societal importance, such as climate change.


Climate change; Climatic changes; Conceptual change; Critical evaluation; Critical thinking; Global warming; Plausibility (Logic); Plausibility judgment; Students; Teaching


Educational Methods | Educational Psychology | Science and Mathematics Education

File Format


Degree Grantor

University of Nevada, Las Vegas




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